The field of mobile communication has witnessed a great revolution over the past two decades, with rapid development of new technologies to satisfy the ever increasing appetite for mobile communication applications and services. Examples of such technologies include CDMA 2000 1xEV-DO systems developed by 3GPP2, WCDMA, HSPA, and LTE systems developed by 3GPP, and mobile WiMAX systems developed by IEEE. Although the current wireless technologies, such as LTE/LTE-A, can provide data rates in the range of tens to hundreds of mega bits per second, their capacity may soon be exhausted by increasing demands for even higher data rates required by data-intensive applications such as video and music streaming. Furthermore, the number of subscribers to mobile communication services (already exceeding 5 billion), is expected to continue to grow rapidly.